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Flipped D300 theory / question

EndlessMtnFab

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It's pretty well known that D300s leak a bit at the rails when flipped. While I absolutely love the MidniteMetalworx case .... I don't have the spare cash for it for my Jeep build. Still need a doubler --- but that's another story.

It's also been somewhat established that leaks are considered un-avoidable. I'd like to challenge that concept and could use some input on my thoughts.

The most common fix is the double-lipped seals in the shift rail house (or bearing cap as some diagrams label it). IMO .... new rails are a must. Whether stainless, or a fancy coated steel, they need to be smooth. That's self-explanatory, but it doesn't always solve the leak. There's enough fluid pushing thru bores of questionable tolerance.

So here's my crazy thought. Why couldn't brass / bronze liners be machined to fit in either the rail house or into the bore of the case itself (maybe even both)? Much like how you can run tighter tolerances on engine valves with exhaust guides, my thinking was to tighten up the slop/clearances so the less oil can even work down to the new double-lip seals.

Don't get me wrong .... I still want a new case. But I am hoping this idea could tide me over and let me use the money for other parts I have not yet acquired.

Any thoughts .... or should I just go fuck myself? :lmao:
 
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EndlessMtnFab

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I'd have to look into what you mean on the gland pack (i know what they are ... but how it could be applied). Someone else already suggested an O-ring, but I wasn't sure how well that could really work without a whole new housing.
 

Lilyota

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I think part of the problem is lateral force. as the rail goes in its being pushed down as as it pulled out its being pulled up.
I thought I had read somewhere once upon a time that you could actually get 2 seals in the box to help mitigate this issue.
 

arse_sidewards

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I think part of the problem is lateral force. as the rail goes in its being pushed down as as it pulled out its being pulled up.
I thought I had read somewhere once upon a time that you could actually get 2 seals in the box to help mitigate this issue.

I've never messed with a 300 but does the rail not have a something to support it at both ends?
 

Mike Honcho

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I think part of the problem is lateral force. as the rail goes in its being pushed down as as it pulled out its being pulled up.
I thought I had read somewhere once upon a time that you could actually get 2 seals in the box to help mitigate this issue.

I use double shift rail seals on my flipped 300. No leaks, knock on wood.
 

SLOWPOKE693

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So as long as they're not too egged out it should be fine?

I think most of the leaking problems on flipped 300's is because of case wear. I bet if we got a brand new D300, installed double lipped seals and flipped it over the case probably wouldn't leak for years. Take a worn out case/rails and do the same thing and you get leaks. IMO that's why some people have no issue flipping one and other people have constant leaks.
 

EndlessMtnFab

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Lilyota ..... I would think the lateral force would apply more with direct connect shifters. Could be wrong. I plan to run cables (since I have 'em) -- so I would hope there aren't forces being appled from other direction. The front bearing cap was the support. The hole is bored thru the aluminum. That was why I was inquiring about a bushing/liner. Can't go straight thru because of the shift pills. But you could do a liner from behind the rails and into the cast housing. Someone pointed out (in private) that liner retention could be a concern. The question is .... is there any benefit to a tighter fit in regard to oil control? Hence my seeking the wisdom :lmao: of Irate members.


1669300358335.png


Mike ..... that was the concern I was having. Half the people do a double seal and everything is dry. The other half still report weeping when sitting for a while. And then you get that one mouthbreather who licks the pavement to clean it up. :laughing: Was just looking up some oil resistant X shaped "o rings."

IMO .... it's still worth a couple of hundred in time/parts/effort. Hopefully we can figure something out.
 

EndlessMtnFab

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I think most of the leaking problems on flipped 300's is because of case wear. I bet if we got a brand new D300, installed double lipped seals and flipped it over the case probably wouldn't leak for years. Take a worn out case/rails and do the same thing and you get leaks. IMO that's why some people have no issue flipping one and other people have constant leaks.

New rails (stainless, perhaps) .... brass liner... and double lipped seals. Would be nice if that did the trick.

If doing new rails .... could make the shift housing part ever so slightly larger (bores & rails) and forgo the liner completely?
 

SLOWPOKE693

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New rails (stainless, perhaps) .... brass liner... and double lipped seals. Would be nice if that did the trick.

If doing new rails .... could make the shift housing part ever so slightly larger (bores & rails) and forgo the liner completely?

I think a bronze liner would be better than going bigger on the bores/rails to tighten up the clearances.
 

fl0w3n

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How bad is the leak? I have a 300 I’m waiting to assemble with a ecobox-i in a flipped configuration, so I’ve yet to experience it.
 

fl0w3n

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Yeah I am with you, I haven’t started anything on mine yet other than collecting the 300 so if there’s something I can do while building it then great. But also, my rig is crusty and cheap so if it’s just a weep and more of a visual nuisance then I don’t think I really care. If we’re talking topping it off every trip and risking it running dry then that’s another story.
 

Winchested

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Hahaha they all leak from every surface. I swear mine leaks everywhere and it was completely resealed. That's not flipped either.
 

EndlessMtnFab

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Hahaha they all leak from every surface. I swear mine leaks everywhere and it was completely resealed. That's not flipped either.

I've been fortunate to have leak free D20s & D300s in the rebuilds I've done. But I haven't futzed with any flipped ones yet. Most of those guys tend to jump to the Atlas instead.
 

EndlessMtnFab

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My God ..... so many kinds of different stainless rods (@ McMaster).


I've ruled out some of the softer/annealed rods. i.e 304
Don't need the high temps. i.e 309/321/330

Saw the High Corrosion 316 .... stronger than 304 and more corrosion resistant. Also see the 17-4 stuff ... but no strength specs.

Any metallurgists care to offer some input before I keep going nuts researching? :beer:

*edit ---- Ruled out 17-4. Less corrosion resistance than 316 despite the extra (apparent) strength.
---- Nitronic 50 & 60 looks ideal. Other than the price. About 100 bucks for 2 feet. :eek:
 
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EndlessMtnFab

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Looking to see what materials the stock rail or Atlas are made from. Obviously different.

Stainless tend to be hard/brittle. But I don't know if twist is really a concern for a shift rail.

*edit --- JB Fabrications uses 17-4 and they heat treat it. Still some question on corrosion resistance and finish.
 
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vetteboy79

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A little aside from your question, but what caused my case to fail was one of the press-in caps on the backside that the rails extend into. It popped out, whether just from vibration, maybe getting oil in it and hydrolocking while shifting, but that let all the oil come out and seized it up on the highway driving back from Area BFE in Moab. I found the cap in the skidplate. Could be as easy as tacking them in place, or maybe some kind glue/sealant...just another failure/leakage point to be aware of.

Beyond that I just shoved two seals into the front bearing retainer and never really had a problem from those.

Are you planning on milling all the slots for the detents and interlock pins in the new rails?

edit: I have a 32-spline AA rear output for a 1980 short-housing case, and a parts case to go with it, and that AA output is set up to be flipped so the vent is in the right orientation. Lemme know if you'd be interested in that.
 

total newb

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Those shit rear caps have always bothered me.

Has anyone bother to make some more substanchle (sp) one and maybe drilled n tapped the case for a retaining bolt?
 

Tech Tim

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Here is a fix someone on the old board did to hold their caps in place:

D300-shift-rail-caps-fix.jpg


That would be pretty easy to replicate.

To make it a little cleaner, I'd make a flat plate that is drilled for an interference fit with the caps. No bends, just one flat plate with the caps sticking through. Chamfer the case holes and an o-ring compressed by the plate for a little more clamping force or maybe epoxy the caps into the plate.
 
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EndlessMtnFab

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Vette ..... Of all things .... I've yet to have a leak from the back caps. Retaining compound and a little bit of luck, I guess. :smokin:

When I contact Jon @ JB --- I'm going to ask how much it would cost for him to make the mods (deeper pocket & longer slot). I'm not 100% sold on the 17-4 yet (as a material). Matte finish is cool and all, but polished would do better for long term rust/corrosion.

Already have the AA rear output installed & redrilled/tapped. Front one is on the last but haven't done anything yet.


Personally ... I've always wondered about tapping the bores for the caps. And then some thin wall tubing chased on the outside. But again ... been lucky with retaining compound.
 
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